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Decapod abundance in the central North Sea 1950-2005

Note: Left: year vs

Data source:

Edwards M. and Richardson A. J., 2004. Impact of climate change on marine pelagic phenology and trophic mismatch. Nature 430: 881884. (left and right) Hadley Centre (http://hadobs.metoffice.com/hadisst/data/download.html) (right)

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Past trends

In the North Sea, work on pelagic phenology has shown that plankton communities, including fish larvae, are very sensitive to regional climate warming with the response to warming varying between trophic levels and functional groups. However the ability and speed at which fish and planktonic communities adapt to climate warming is not yet known. In other European regional areas, long-term data on marine phenology changes are quite sparse. According to some preliminary studies, there has also been some phenological movement in certain copepod species in the Mediterranean Sea over the past decade (Juan-Carlos Molinero, pers. com.).
Due to the sensitivity of their physiological development to temperature, decapod larvae were selected as representative of phenological changes in shelf-sea environments (Lindley, 1987). The zooplankton growing season indicator shows the annual timing of peak seasonal abundance of decapod larvae from 1958-2005 in the central North Sea (Figure 1 left). A shift towards an earlier seasonal peak is clearly visible. In particular, since 1988, the seasonal development of decapod larvae has occurred much earlier than the long-term average (baseline mean: 1958-2005) - in the 1990s up to 4-5 weeks earlier than the long-term average This trend towards an earlier seasonal appearance of decapod larvae during the 1990s is highly correlated with sea surface temperature (Figure 1 right).

Projections

Projections of how individual species react to future climate change have not yet been made, but the empirical evidence suggests that it is very likely that phenological changes will continue to occur as climate warming continues to accelerate. It is currently much less certain to what degree genetic adaptations within species populations can cope with these changes and whether the current pace of climate warming is too fast for genetic adaptations to take place.